FOR u IN users
  LET friends = (
    FOR f IN friends 
      FILTER u.id == f.userId
      RETURN f
  )
  LET memberships = (
    FOR m IN memberships
      FILTER u.id == m.userId
      RETURN m
  )
  RETURN { "user" : u, "friends" : friends, "numFriends" : LENGTH(friends), "memberShips" : memberships }